by Erin Marissa Russell
If you’re planning to grow your tomato plants in containers or a raised bed garden, or if you need to move your tomato plants and want to do so without damaging their roots, you’ll need to know how far the roots of tomato plants extend into the soil. Keep reading to learn about just how deep into the grown the roots of your tomato plants grow.
How Deep Does a Tomato Plant’s Root System Go?
As dicots, or plants that have two embryonic leaves (called cotyledons), tomatoes have a taproot system. This is in contrast to the fibrous root system of monocots, plants that have just one embryonic leaf. A fibrous root system is what you normally imagine when you think of a plant’s roots: a network of lots of small, branching roots that look something like the branches of a tree turned upside down.
In contrast, a taproot system has some of those small, branching roots, but right in the center is the taproot. The taproot is larger than the other roots that support it and burrows deep into the soil so it can absorb lots of nutrition and water. When there are no obstacles in its way, a taproot will tunnel straight down into the soil.
The taproot of a tomato plant can extend as far down into the soil as three feet. Long taproots like this are especially prone to forming when the plant needs to cover more ground in order to get the hydration and nutrients it requires to grow healthy and strong. That’s why you’ll see the longest taproots in tomato plants that grow in poor, loose soils.
What Factors Affect the Depth of a Tomato Plant’s Roots?
Of course, not all varieties of tomato plant are created equal. Some plants create strong taproot that support the plant by providing plenty of nutrients and water. Other tomato plants have weaker root systems, in which the taproot doesn’t stretch as far into the ground. These tomato varieties will depend more on the gardener to supply the plant with the water it needs or to provide fertilizer to round out its nutritional requirements. There are other factors that will influence the depth of a tomato plant’s root system as well.
When a tomato plant is grown in a container or a raised bed, the depth of the soil available to it will naturally affect how far into the ground its taproot can stretch. When the taproot is prevented from tunneling down into the soil by a container or the bottom of a raised bed planter, it’s common for the taproot to grow in circles on the bottom surface of the container or planter.
Even though the tomato plant won’t get any additional hydration or nutrients from the taproot encircling the same area multiple times, the plant is biologically driven to continue extending the taproot. When it’s possible to breach the boundary at the bottom of a raised bed planter, tomato plants have been known to continue tunneling down into the soil below in their search for nutrition.
The type of soil in which a tomato plant is growing will also influence how far its taproot extends. As we’ve already mentioned, the maximum taproot length is seen in poor or loose soils. If the soil in your garden is extremely dense and compact, your tomato plant may not be able to make its way far into the depths of the soil. In this case, just as it does in a container, the taproot will continue to grow laterally.
Your soil quality impacts the growth of your tomato plant’s root system in another way as well. When the soil is especially rich and fertile, your tomato plant doesn’t really need to extend its taproot far down into the soil in order to acquire the nutrients it needs to support the plant’s growth. Under these circumstances, the root system will still develop, but it will look different.
When soil is particularly healthy, the roots won’t spread out as widely and will have a denser, more compact formation. The plant will devote more of its energy to developing the secondary roots that branch off from the taproot, and as a tradeoff the taproot itself will not be as fully developed. Tomato plants that grow in soil like this will have a wider root system that doesn’t stretch as far down into the ground as a tomato plant’s taproot would normally grow.
Some gardeners use a technique when they grow tomato plants that involves burying the stem partially under the surface of the soil. This works because tomato plants can grow roots from their stem. When this technique is utilized, the greater capacity for root growth means that the tomato plant doesn’t need to depend on its taproot as much since it has the support of these additional roots from the stem. As a consequence, the taproot may not delve as deep into the soil in these cases.
Now you know how deeply the taproot of a tomato plant normally extends under the ground. You’ve also learned the various factors that can influence how well developed the root system of your tomato plants becomes. Now that you’ve read this article, you should be prepared to transplant tomatoes without cutting into their roots or to provide them with containers and raised beds that give their taproots plenty of room to grow.